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| author | Joerg Roedel <jroedel@suse.de> | 2019-06-24 10:23:16 +0200 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2019-06-24 10:23:16 +0200 |
| commit | ceedd5f74d8cfe34db4e654a7808e3c5de40d6f5 (patch) | |
| tree | e19c18292231202e9cd8d484ee43f46b2c9c9ad1 /arch/x86/entry/vdso/vclock_gettime.c | |
| parent | 1b961423158caaae49d3900b7c9c37477bbfa9b3 (diff) | |
| parent | 4b972a01a7da614b4796475f933094751a295a2f (diff) | |
Merge tag 'v5.2-rc6' into generic-dma-ops
Linux 5.2-rc6
Diffstat (limited to 'arch/x86/entry/vdso/vclock_gettime.c')
| -rw-r--r-- | arch/x86/entry/vdso/vclock_gettime.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c index 98c7d12b945c..4aed41f638bb 100644 --- a/arch/x86/entry/vdso/vclock_gettime.c +++ b/arch/x86/entry/vdso/vclock_gettime.c @@ -1,6 +1,6 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * Copyright 2006 Andi Kleen, SUSE Labs. - * Subject to the GNU Public License, v.2 * * Fast user context implementation of clock_gettime, gettimeofday, and time. * @@ -128,13 +128,24 @@ notrace static inline u64 vgetcyc(int mode) { if (mode == VCLOCK_TSC) return (u64)rdtsc_ordered(); + + /* + * For any memory-mapped vclock type, we need to make sure that gcc + * doesn't cleverly hoist a load before the mode check. Otherwise we + * might end up touching the memory-mapped page even if the vclock in + * question isn't enabled, which will segfault. Hence the barriers. + */ #ifdef CONFIG_PARAVIRT_CLOCK - else if (mode == VCLOCK_PVCLOCK) + if (mode == VCLOCK_PVCLOCK) { + barrier(); return vread_pvclock(); + } #endif #ifdef CONFIG_HYPERV_TSCPAGE - else if (mode == VCLOCK_HVCLOCK) + if (mode == VCLOCK_HVCLOCK) { + barrier(); return vread_hvclock(); + } #endif return U64_MAX; } |